1) Field of the Invention
The present invention relates to a coated film peeling/removing apparatus for coated resin products, bumpers, side lacings for a vehicle, CD-ROM or the like used electronic appliances. Further, the present invention relates to a peeling/removing method of the coated film.
2) Description of the Prior Art
In recent years, serious consideration has been given to recycling of resin product due to mounting interest in environmental problems and reutilization of sources (materials, natural resourses). Attention has been given to recycling of resin products removed from discarded vehicles and discarded products. The problems are particularly intense for used products such as bumpers, side lacings or similar resin products produced by the vehicle industry.
The surface of this kind of resin products such as bumpers, side lacings or the like is usually coated with surface treatment materials for improving appearance and quality. In general, a film is coated on the surface of the bumpers made from thermoplastic resin materials such as polypropylene based resin or the like after applying a primer composed of thermoplastic resin such as polypropylene based resin or the like. The material of this coated film is a thermosetting resin, e.g., an amino polyester based resin, an amino acrylic based resin, an amino polyester urethane based resin or an acrylic urethane based resin. These resins are liquid before the hardening reaction but a bridge structure is formed in the film by a baking finish. Since the structure is strong and dense, the coated resin bumper has excellent chemical resistance, heat resistance, scratching resistance, weather resistance and excellent surface brightness.
When the coated bumper is crushed in this condition for pelletizing, coated film pieces are mixed in the raw material of the resin product composed of polypropylene based resin. When molded into polypropylene based resin, the coated film pieces obstruct flowability of the molten resin, causing "burn", "weld mark", "bubbles" or a similar flowed moldings to occur. Another drawback is that the coated film pieces float up to the surface of the resin product which degrades the appearance of the resin product.
The coated film pieces are thermosetting resin and the polypropylene based resin serving as the base resin is a thermoplastic resin so that little mutual interaction occurs between the coated film pieces and the base resin, and the coated film pieces which can not be finely dispersed in the base resin prevents the recycled resins from being integrally kneaded, resulting in remarkably deteriorated mechanical properties of the recycled resin product. Consequently, the usable range of the recycled resin product is largely restricted.
For this reason, removal of the coated film is absolutely necessary in the case that the resin products are recycled with the coated resin products. As disclosed at page 3 to 9, NO. 5, Vol. 46, in Technical Booklet "Automobile Technology" edited and published in 1992 by the "Automobile Technology Association", of Japan, there are many mechanical, physical and chemical methods for peeling and removing the coated films from the coated resin product.
As the mechanical coated film removing method, there is a shot blasting method of blowing fine granular abrasive material toward the coated surface of the resin product to break the coating and then removing the broken coated resin, and a screen mesh method of removing coated film pieces mixed but not disssolved in the molten resin after finely crushing the resin product, melting the finer crushed product and filtering coarse resin roducts by extruding through a screen mesh.
The shot blasting method is acceptable from the viewpoint that poisonous substances are not scattered and environmental safety is secured. However large shot blast equiment is required and coated film removing efficiency is not satisfactorily high. It is especially very difficult to apply this method for concaved, recessed or irregularly protruded parts. The screen mesh method although acceptable from the viewpoints as mentioned above, however, there arises a problem clogging because the screen mesh is clogged with undissolved coated pieces, causing extrusion force to be greatly increased. The results in extrusion quantity and productivity being degraded. Thus, the coated film can not be removed at a sufficiently high efficiency. Another drawback is that there often arises a necessity for replacing the screen mesh with a new one when the screen mesh is clogged with the coated film pieces, resulting in low production efficiency.
The physical removing method of the coated film uses a halogen based solvent or various kinds of organic solvents. A phenomenon of penetration of solvent into the boundary between the coated film and raw material or a phenomenon of expansion of the coated film is utilized for removing the coated film. However, this method is unacceptable from the viewpoint as mentioned above, and the coated film removing efficiency and the treatment capacity are comparative low, and moreover, there is a problem that the characteristics of the raw material may change.
As the chemical coated film removing method, there is known an organic acid salt method of chemically dissolving and removing the coated film by cutting an ether bonding in the proximity of a bridge point of the resin to be peeled in an ethanol aqueous solution containing, e.g., an organic salt.
This coated film removing method has a problem which requires a secondary treatment such as waste water treatment or the like, and moreover, the treatment efficiency is low and inefficient.
In addition, as an apparatus for removing coated film of a resin product, there is shown a prior art apparatus for peeling the surface of synthetic resin as shown in FIG. 22 that is an illustrative front view and disclosed in an official gazette of Japanese Patent Laid-Open Publication NO. 5-337941.
The peeling apparatus is such that a resin product, e.g., a side lacing 102 is conveyed between rotary members 103 and 104 each composed of a foamed synthetic resin by a pair of conveying rollers 101, and a conveying speed V of the side lacing 102 is lower than the rotational peripheral speed of the rotary members 103 and 104 so that cutting and high frictional forces are exerted on a coated film 102a of the side lacing 102 and a double sided adhesive tape 102b so as to cut and peel the coated film 102a of the side lacing 102 and the double sided adhesive tape 102b, and moreover, convey the side lacing 102 by a pair of conveying rollers 101.
With this peeling apparatus, since the rotary members 103 and 104 each composed of a foamed synthetic resin comes in contact with the resin product, the rotary members 103 and 104 are broken due to the brittleness while generating powder dust. For this reason, the peeling apparatus is not preferable from the viewpoint of working environment. Another drawback is that this peeling apparatus is not suitable for a bent or curved resin product.